I don't disagree with creators of artistic works seeing ways to improve or add on to things as times and technologies change, but don't you find it interesting that it's more typical of a writer to make changes to past works (eg add things like King), while visual artists who use static mediums like paintings, while typically never satisfied, rarely will go back and change something? That and painters are finicky... I'm not saying that is an absolute, but it just seems to be more prominant.
Are you sure that's the case, though? I don't follow art much, but I have the impression there are at least some instances of an artist doing multiple versions of a given painting or sculpture, or making replicas of an earlier work. I imagine an art historian or expert could speak to whether they modified their brushstrokes, the details of the work, and so on.
After all, when writers go back and rewrite a novel or story, they're creating a new edition of the work, just like a painter or sculptor who creates a replica of the original. So it wouldn't be analogous to going back to the original portrait and painting over it, say. Even what George Lucas did with the Star Wars
films is making a new, distinct edition, although he's tried to suppress the earlier editions.